"This week." Brink of war. Russian forces take crimea. Parliament authorizes a strike on ukr with the world on high Aler will Vladimir Putin expand his invasion? There will be costs for the military intervention in the Ukraine. What will those costs be? Does president Obama have what it takes to prevent war. This morning, answers from secretary of state John Kerry and our experts from the danger zone. Plus live reports from the danger zone. Culture clash. That hot button bill in Arizona. A water shed moment in the fight for gay rights? Our powerhouse roundtable take on that debate and all the week's politics. Plus Mr. Affleck goes to Washington, and Nate silver cracks the Oscar code. All right here this Sunday morning. As we come on the air this morning, America and the west are facing the most perilous confrontation with Russia since the cold war. President Obama spent a tense 90 minutes on the phone with Vladimir Putin yesterday, warning him to withdraw from the Ukraine. The unsecurity council has been meeting in an emergency session, but Russia is not backing down. On the move, surrounding Ukrainian military bases. The new Ukrainian government put its forces on display too. It's a high-stakes and dangerous standoff. We have Alex Marquardt in crim crimea. Reporter: When the U.S. Says Russia has invaded, this what they mean. They have circled this base, demanding their surrender. Russia this morning tightening its grip. A dangerous standoff in crimea, these troops lining the outer wall of a Ukrainian naval base. No one going in or out. At another base this it commander said he was told twice to surrender. But he said his orders were to hold the base and he was ready to fight. They have been on the move in crimea. It's a region of Ukraine home to the black sea fleet and a mostly-russian population. The U.S. Says it's a Russian invasion and occupation, and demanding that troops withdraw. The U.N. Security council met in an emergency session yesterday. It's time for the Russian intervention in Ukraine to end. The Russian military must stand down. Reporter: During a 90-minute call on Sunday, president Putin told president Obama that Russia has the right to defend its interests and Russian people. Other international leaders joined with the U.S. British prime minister David Cameron saying there's no excuse. Canada recalling their ambassador from Moscow. This as pro-russia fervor sweeps eastern Ukraine. Flags torn down from government buildings, pro-russia protesters savagely beating those who support Ukraine's new government. Ukraine now more divided than ever. And the prospect of war growing ever closer. It's now a high-stakes gate waiting to see who moves next. Will Russia complete the take over and possibly other parts or bow to American and international pressure? George. That is the question. Vladimir Putin's intervention echoes previous military moves into former soviet republicans like Georgia. This is a serious challenge to America and the west. What is behind the movies? Where will we go next? Terry Moran has more. Reporter: In just a few dramatic days, Vladimir Putin has shown the world two sides of as I dominating style as leader of Russia. First there was sochi. The olympic games were Putin's personal project, seven years of work, $50 billion spent all to send a single overriding message. As he told George stephanopoulos just before the games began. Translator: I would very much like during the olympics for the athletes, visitors, reporters and those who will follow the olympic on TV through the media for people to see a new Russia. Reporter: Then came Ukraine. After revolution in kiev, Russian tanks, choppers and troops moved into crimea. An older, darker image of Russian power. But Putin has done this before. 2008, Russian troops invade the neighboring nation of Georgia. He claims he is defending ethnic Russians there. The same rationale for the move in Ukraine. The U.S. And oourn european allies object, but six years later, Russian troops remain in Georgia. And now he is telling the world he is willing to use military force in Ukraine and risk a conflict with the U.S. And the west. We are on the edge of the not cold war, but we're on the edge. Reporter: Here's why. Ukraine is divided. Kiev and the rest of the country yearn to join Europe and the U.S. And forge a different future. While in crimea and the east where so many ethnic Russians live, they look to Moscow. And they have used crimea as a major Russian naval base for 200 years. On Friday, Obama tried to send his own message to Putin. He There'll be costs for military intervention in Ukraine. Reporter: Hours later, Russian troops were on the move and Putin was there. It's clear that maybe the president of the United States has been a bit naive about him and his ambitions. Reporter: George W. Bush did no better managing Putin, even though he declared he looked into his soul. But he cares about being feared and restoring Russian greatness. The next move, solidify control over crimea, and make sure that Ukraine never moves too close to the west. Or else.

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